In Stouffer Pat. No. 4,250,799, (incorporated herein by reference) assigned to the assignee hereof, there is disclosed a sweeping air stream apparatus and method in which air flow under pressure through a channel to an outlet element is caused to issue as a sweeping air stream pattern by a resilient vane or reed oscillator element having a free upstream end and a secured downstream end which is rendered oscillatable between a pair of extreme positions solely by air flow and, in Stouffer application Ser. No. 119,699 filed Feb. 8, 1980 entitled "Oscillating Reed and Method",(incorporated herein by reference), also assigned to the assignee hereof, the oscillator is disclosed as having a resilient vane or reed which incorporates means for limiting the bending thereof to an axis transverse to the direction of flow, said limiting means being constituted by one or more bends in the body of the resilient vane member to reduce the amount of noise produced. As there disclosed, the fluid air stream can and does at times distort the bending axis of the reed thereby creating a noise or clicking sound, such noise being very undesirable in air distribution systems and because of the distortion in the spring tending to reduce the life of the element when used as an oscillator. In addition, in his application Ser. No. 119,699 now U.S. Pat. No. 4,336,909, Stouffer suggested a series of transverse corrugations along the entire length of the body of the element to achieve the same objective as the general curvature or bend, as well as using a series of stiffner elements based along the entire operating length of the reed body. An alternative structure is disclosed in Stouffer International Application No. PCT/US80/00368 filed Apr. 9, 1980 and entitled "Sweeping Air Stream Apparatus and Method", (incorporated herein by reference), also assigned to the assignee hereof, wherein, in addition to the prior Stouffer disclosures referred to herein above, the resilient reed oscillator element comprised a pair of spaced apart elongated coil springs with an elastomeric sheet supported on the coil springs with the weight member being on one end of the pair of coil springs.
The above constitutes the best prior art and is referred to in compliance with 37 CFR .sctn.1.56, 1.97 and 1.98 and the duty of candor required by the Patent Laws of the United States. A text entitled "Technology of Carbon and Graphite Fiber Composites" by John Delmonte, Vans Nostrand and Reinhold Company, Copyright 1981 is also referred to for background information on carbon and graphite fiber composites as used in the preferred embodiment of the invention.
The present invention is an improvement over the above-identified Stouffer inventions in that there is amplitude modulation, i.e. the oscillation amplitude is insensitive to wide ranges of air flow rates, fatigue strength is improved and there is a reduction in noise from the buckling and the initiation of oscillation is easier.
According to the preferred embodiment of the present invention, graphite composite strips are assembled in spaced relation with the downstream ends secured in a mounting structure and the upstream ends secured to a common weight element. The graphite reeds are made from graphite fibers bound together by an epoxy resin matrix which can be reinforced by a scrim of fiber glass and a polyester resin. The graphite fibers are parallel to each other and perpendicular to the axis of bending so that the fibers are oriented to adequately resist the flexure bending (compression and tension). While it is within the contemplation of this invention that there be layers of fibers which are oriented to resist forces normal to the flexure and to the flexure axis, according to the preferred embodiment of the present invention, the torsion force or moment is resisted by the epoxy resin and by the glass scrim, if any. In the preferred embodiment, buckling due to these small torsional moments which cause noise is avoided by a plurality of undulations, the frequency of said undulations being sufficient to reduce the noise. The graphite fiber reinforced reed has greatly enhanced fatigue strength. In addition, the strip reed elements are not over driven when air velocity and flow rate are increased. Reed oscillation amplitude modulation is important because it solves the problem that the air flow in some cars for cold defroster operation is much greater than in hot defroster operation. A flat integral reed would start and operate in hot defrost and would twist and bang around violently in cold defrost operation. Thus by modulating the amplitude of oscillation by making the amplitude much less a function of air flow rate the strip reed elements construction is not over driven at higher air flow rates.